Companies often employ multiple destination servers on a network, each equally capable of responding to requests for information. Generally, a load balancer on the network may route such requests for information to one of these destination servers on the network based on any number of considerations. For example, if a client computer makes a request for information to which each of the destination servers on the network are capable of responding, the load balancer may route the request to the destination server that the load balancer considers to have the most availability.
The load balancer may receive measurements about the destination servers and determine how to route the requests based on these measurements. For example, probes distributed across the network may gather measurements about states at each destination server such as the traffic load, CPU load, response time, etc., and may send these measurements to the load balancer at regular intervals. The load balancer may then use these measurements to determine where to route requests for information.
Various delays inherent in the network, however, may cause these measurements to be stale by the time they are used by the load balancer. That is, the probe measurements (e.g., traffic load, CPU load, response time, etc.) may not accurately represent the present state of each of the destination servers, but instead may represent some past state that has changed since it was measured by the probe. For example, the measurements used by the load balancer may become stale due to the time between measurement intervals, the time it takes to propagate the measurement data from the destination server to the probe and from the probe to the load balancer, or any other delay that results in the reported measurements not reflecting the current state of the destination server.
Thus, conventional load balancing systems may not be able to properly, or at least optimally, route requests for information to two or more destination servers because the measurements used to determine how the requests are being routed may not reflect the current state of the destination servers. One way to reduce the problem of stale data is to make measurements at more frequent time intervals. This approach, however, may increase the load on the destination servers and may be computationally expensive for both the probes and the load balancers. Thus, another way is needed to effectively route requests using the load balancer that does not increase the load on the destination servers, while still ensuring that the measurement data being used by the load balancers is not stale.